Adrenal Glands, Pineal Gland, and Pancreas Flashcards

Flashcards covering the physiology of the adrenal cortex and medulla, the pineal gland's role in circadian rhythms and DNA repair, and the pancreatic control of blood glucose.

Adrenal Cortex

The outer part of the adrenal gland divided into three layers based on the arrangement of endocrine cells.

Zona glomerulosa

The outermost layer of the adrenal cortex, named for its tangle-like cell arrangement, which produces mineralocorticoids.

Mineralocorticoids

A group of hormones that affect ions (minerals), specifically sodium ($Na^+$) and potassium ($K^+$).

Aldosterone

The primary mineralocorticoid made in the zona glomerulosa that promotes sodium reabsorption and potassium excretion in the kidneys.

Zona fasciculata

The middle layer of the adrenal cortex where endocrine cells are organized into long columns called fascicles; it primarily produces glucocorticoids.

Glucocorticoids

Hormones such as cortisol that regulate glucose metabolism and help the body deal with chronic or prolonged stress.

Zona reticularis

The innermost layer of the adrenal cortex characterized by a network-like arrangement of cells that produces sex hormones (androgens).

Corticotropin-releasing hormone (CRH)

A hormone released by the hypothalamus that travels through the portal system to stimulate the anterior pituitary.

Adrenocorticotropic hormone (ACTH)

A peptide hormone released by the anterior pituitary that targets the zona fasciculata to stimulate the release of glucocorticoids.

Transcortin

A specific alpha globulin plasma protein that carries approximately 75% of glucocorticoids in the blood.

Albumin

An abundant plasma protein that carries about 25% of glucocorticoids in the blood and is also found in synovial joints.

Glucocorticoid response elements

Specific regions in the DNA where the glucocorticoid-receptor complex binds to act as a transcription factor.

Gluconeogenesis

The process of taking amino acids and glycerol to turn them into glucose; stimulated by glucocorticoids.

Lipolysis

The breakdown of lipids to produce fatty acids, which is increased by glucocorticoids.

Cytokine

A signaling molecule used in the immune system; its release is decreased by glucocorticoids.

Hyponatremia

A condition of low blood sodium ($Na^+$) that stimulates the release of mineralocorticoids.

Hyperkalemia

A condition of high blood potassium ($K^+$) which can stimulate the release of aldosterone.

Renin

A protease enzyme made by granular cells in the kidney that converts angiotensinogen into angiotensin I in response to low blood pressure.

Angiotensinogen

A precursor protein constitutively produced by the liver and released into the plasma.

Angiotensin-converting enzyme (ACE)

An enzyme highly abundant in the lungs that converts angiotensin I into angiotensin II.

Angiotensin II

A peptide hormone that causes vasoconstriction, stimulates ADH release, triggers thirst, and stimulates aldosterone release.

Distal convoluted tubule

The part of the kidney where aldosterone works to increase sodium reabsorption via sodium channels and sodium-potassium ATPases.

Chromaffin cells

Modified postganglionic neurons in the adrenal medulla that release catecholamines (75% epinephrine, 25% norepinephrine).

Pineal gland

A gland posterior to the hypothalamus that produces melatonin, primarily during darkness.

Suprachiasmatic nucleus (SCN)

A hypothalamic nucleus located above the optic chiasm that receives light input from retinal ganglion cells to regulate biological rhythms.

Tryptophan

The amino acid from which melatonin and serotonin are derived.

Soporific

A term describing a substance, such as melatonin, that makes it easier to fall asleep.

Reactive oxygen species

Byproducts of oxidation-reduction reactions that can cause damage to DNA; repaired during periods of high melatonin.

Pancreatic islets

Little islands of endocrine cells (alpha, beta, delta) located within the exocrine tissues of the pancreas.

Beta cells

Cells in the pancreatic islets that produce and release insulin in response to elevated blood glucose.

Alpha cells

Cells in the pancreatic islets that produce and release glucagon in response to low blood glucose.

Insulin

A 51-amino acid protein hormone with two polypeptide chains that promotes glucose uptake and storage as glycogen.

Glucagon

A 29-amino acid peptide hormone that stimulates glycogenolysis and gluconeogenesis to raise blood sugar.

Glycogenolysis

The breakdown of glycogen to produce glucose.

Humoral stimulus

A stimulus for hormone release based on changes in body fluids, such as blood glucose or ion concentrations.